From the resonant frequency of the material in longitudinal, transverse, and
torsional modes, Poisson's ratio ([upsilon]) can be computed from test
data. Foundation response to dynamic loading, and the effect of wave energy
on its surroundings is studied in the light of these test results. The
ultrasonic pulse test also evaluates the two moduli and Poisson's ratio, but
the test results are more reliable for rocks than for soils.
Dynamic tests can be run on undisturbed or compacted samples, but
should be run only if the particular project really requires them. The
number of tests depends on project circumstances. Estimates of dynamic
parameters can be obtained from correlations with other properties (see
references in Section 6 of this chapter).
f. Compaction Tests. In prospecting for borrow materials, index tests
or compaction tests may be required in a number proportional to the volume
of borrow involved or the number of samples obtained. Structural properties
tests are assigned after borrow materials have been grouped in major
categories,by index and compaction properties. Select samples for
structural tests to represent the main soil groups and probable compacted
condition.
At least one compaction or relative density test is required
for each significantly different material (based on gradation or
plasticity). Numbers of other tests depend on project requirements.
g. Typical Test Properties. Various correlations between index and
structural properties are available showing the probable range of test
values and relation of parameters. In testing for structural properties,
correlations can be used to extend results to similar soils for which index
values only are available. Correlations are of varying quality, expressed
by standard deviation, which is the range above and below the average trend,
within which about two-thirds of all values occur. These relationships are
useful in preliminary analyses but must not supplant careful tests of
structural properties. The relationships should never be applied in final
analyses without verification by tests of the particular material concerned.
Section 2.
INDEX PROPERTIES TESTS
1. MOISTURE CONTENT, UNIT WEIGHT, SPECIFIC GRAVITY. Index properties tests
are used to compute soil volume and weight components (Table 6).
Ordinarily, determine moisture content for all the representative samples
(disturbed or undisturbed) for classification and grouping of materials in
principal strata. See Table 1 for test standards.
a. Unsaturated Samples. Measure moisture content, dry weight, specific
gravity, and total volume of specimen to compute volume-weight
relationships.
b. Saturated Samples. If moisture content and dry weight are measured,
all volume-weight parameters may be computed by assuming a specific gravity.
If moisture content and specific gravity are measured, all volume-weight
parameters may be computed directly. Volume-weight of fine-grained soils
below the water table may be determined with sufficient accuracy by assuming
saturation.
7.1-134
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